Application of differential staining techniques and continued improvement of established methods are basic to all of the projects conducted in the laboratory. Human cytogenetic studies of patients with congenital and developmental disorders as well as studies of mutagen-induced chromosomal abnormalities are continuing. Murine cytogenetic studies include evaluation of mitotic and meiotic chromosomes of Robertsonian translocation carriers and karyotypic evaluation of cells in hematopoietic tissue regeneration experiments. Immunogenetic and cytogenetic characteristics are also being studied in NZB and DBA mice. These are part of projects utilizing the mouse as a model for human diseases. BIBLIOGRAPHIC REFERENCES: Brecher, G., Tjio, J.H., Smith, W.W., and Haley, J.E.: Marrow regeneration after mechanical depletion. Blood 48: 679-686, 1976. Raveche, E. S., Klassen, L. W., and Steinberg, A. D.: Sex differences in formation of anti-T-cell antibodies. Nature 263: 415-416, 1976.